The present invention relates to isolated phase bus assemblies and more particularly to a novel separable plug joint assembly for coupling or plugging together isolated phase bus housing sections.
Isolated phase bus systems are well known in the art of power transmission and distribution. Isolated phase bus systems typically comprise a plurality of isolated phase bus sections electrically connected end-to-end. Each section is provided with a central or interior conductor operated at an elevated voltage level and a conductive metal outer housing surrounding and concentric with the interior conductor, which outer housing is normally maintained at or near ground potential. The end-to-end sections in conventional isolated phase bus runs are normally coupled together and sealed by housing covers which are welded to the adjacent housings in the field.
While most runs of isolated phase bus duct systems occur in relatively open environments where it is easy to field install the housings and couplings, this is not the case in closed environments where there is restricted access to the bus duct to couple sections together in the field. Further, any coupling of the bus duct sections by housing covers that increase the diameter of the housing structure provides either a field accessibility problem or results in the enclosure having to be enlarged to house the bus duct runs.
For example, the use of bus duct runs through the shaft of a rotary transformer is contemplated to carry collector current to the rotor of the transformer. The diameter of the shaft is related to the placement of the bus duct runs in the shaft and the outside diameter of these bus duct runs because minimal distances are required between the shaft and the bus duct runs to prevent arcing and shaft heating from magnetic effects of currents carried by the bus duct runs. In this enclosed environment, it is advantageous to maintain the shaft diameter to a minimum. In this example, 3 phase isolated bus duct runs pass through the center of the shaft and the shaft is split into sections for field servicing. The bus duct runs are also split into two sections and must be coupled together within the shaft sections. Accordingly, any coupling that increases the over all diameter of the bus runs may result in restricted access to the coupling within the shaft or an increase in the shaft diameter to accommodate the 3 phase isolated bus duct runs.
While many forms of bus duct run connectors have been developed, many of these connections involve plug or stab connections or fingers with exterior mounted springs and bolts connections between the interior conductors. These connections are usually unshielded and have a larger diameter than the diameter of the interior conductors. Consequently, the outer housing coupling diameter must be increased to maintain acceptable distances between the inner conductor coupling and the outer conductive housing. In environments where there is an enclosure around the bus duct, any increase in the outer dimension of the inner conductor coupling reduces the electrical clearances to the enclosure and the enclosure has to be made larger to distance the interior wall further from the bus duct outer housing wall.
The present invention relates to an isolated phase bus duct coupling suitable for use in enclosed environments.
The present invention relates to an isolated phase bus duct coupling that is separable and readily serviceable.
The present invention further relates to isolated phase bus duct couplings suitable having minimal increased outside diameters at the coupling for the inner conductors.
The present invention relates to an isolated phase bus duct joint assembly for coupling together first and second phase bus duct sections. Each section comprises an interior bus conductor surrounded by an outer housing. The joint assembly couples end portions of the interior bus conductor by the use of spring loaded fingers that extend between the end portions of the interior bus conductors. The fingers are electrical contact members mounted to a coupling end portion of one of the interior bus conductors and the spring biases the fingers into contact with both end portions of the interior bus conductors. The springs are positioned within the inner bus conductors so as not to increase the outside diameter or dimension of the interior bus conductors at the coupling assembly. Preferably, the coupling end portions of interior bus conductors are of a reduced outside dimension so that mounting of the finger contact members to the outside surface of the coupling end portions minimizes any increase in outer dimension of the interior bus conductor at the coupling assembly. This advantageously results in no substantial increase in electrical clearance required between the inner bus conductors and the outer housing.
In an aspect of the present invention there is provided an isolated phase bus duct joint assembly for coupling together first and second phase bus duct sections. Each section comprises an interior bus conductor surrounded by an outer housing. The joint assembly comprises first and second conductor coupling portions each extending from the end portion of one of the interior bus conductors. Each of the coupling portions has inside and outside surfaces. The joint assembly comprises a plurality of movable contact fingers mounted around the outside surface of the first conductor coupling portion, each by spring loaded adjustment fasteners. Each of the fingers extends beyond the first conductor coupling portion for engagement with the outside surface of the second conductor coupling portion. Each of the spring loaded adjustment fasteners comprises a threaded stem passing through the finger and the first inner conductor coupling portion. The stem has an adjustable head engaging an outer surface of the finger and a spring, preferably compression, mounted over the stem to engage the inside surface of the first inner conductor coupling portion. The head and stem are adjusted relative to the spring to urge the finger into locking engagement with the first and second coupling portions.
Preferably, the outside surface of the first and second inner conductor coupling portions has an outside dimension reduced relative to conductor outside surfaces of the interior bus conductors. Further, the interior bus conductors of each section and the first and second inner conductor coupling portions are cylindrical in shape and the first and second inner conductor coupling portions each have a diameter reduced relative that of the interior bus conductors.
Preferably, the first and second conductor coupling are mounted within the end portion of one of the interior bus conductors and are of complementary shape with the interior bus conductors.
The coupling assembly preferably further includes a sheath attached to one of the inner conductors and extending over and spaced from fingers over the other inner conductor by a predetermined amount. The sheath has a reduced diameter forming an annular flange that fits onto the one said inner conductor. The sheath is held relative to the one inner conductor by a bead of sealant between the annular flange and one inner conductor.
The outer housing of the bus duct sections may be joined in any suitable manner. The joint may be aligned with the coupling or preferably slightly axially displaced relative to the coupling of the interior bus conductors. Preferably, the joint outer housings are joined by abutting flanges coupled by fasteners. Further an insulator is located between these flanges and the insulator extends towards the interior bus conductors to surround and support the sheath.
It should be understood that the teaching of the present invention are equally applicable to couplings that are curved or spherical in shape to have the joints located at a corner in the bus duct run. The preferred application is for two runs of bus duct extending along the same axis or closely adjacent parallel axes.
For a better understanding of the nature and objects of the present invention reference may be had to the accompanying diagrammatic drawings in which: